Computational wafer inspection

ABSTRACT

A defect prediction method for a device manufacturing process involving processing a portion of a design layout onto a substrate, the method including: identifying a hot spot from the portion of the design layout; determining a range of values of a processing parameter of the device manufacturing process for the hot spot, wherein when the processing parameter has a value outside the range, a defect is produced from the hot spot with the device manufacturing process; determining an actual value of the processing parameter; determining or predicting, using the actual value, existence, probability of existence, a characteristic, or a combination thereof, of a defect produced from the hot spot with the device manufacturing process.

This application is a continuation of U.S. Patent application Ser. No.15/996,992, filed Jun. 4, 2018, now allowed, which is a continuation ofco-pending U.S. patent application Ser. No. 15/339,669, filed Oct. 31,2016, now U.S. Pat. No. 9,990,462, which is a continuation of U.S.patent application Ser. No. 14/730,993, filed Jun. 4, 2015, now U.S.Pat. No. 9,507,907, which claims the benefit of priority under 35 USC §119(e) of U.S. Provisional Patent Application No. 62/010,221, filed Jun.10, 2014, and of U.S. Provisional Patent Application No. 62/023,589,filed Jul. 11, 2014, each of the foregoing applications is herebyincorporated in its entirety by reference in the present disclosure.

FIELD

The present description relates to a method of optimizing theperformance of semiconductor manufacturing process. The method may beused in connection with a lithographic apparatus.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a target portion of a substrate. Lithographic apparatus can beused, for example, in the manufacture of integrated circuits (ICs). Inthat circumstance, a patterning device, which is alternatively referredto as a mask or a reticle, may be used to generate a circuit patterncorresponding to an individual layer of the IC (“design layout”), andthis pattern can be imaged onto a target portion (e.g. comprising partof, one or several dies) on a substrate (e.g. a silicon wafer) that hasa layer of radiation-sensitive material (resist). In general, a singlesubstrate will contain a network of adjacent target portions that aresuccessively exposed. Known lithographic apparatus include so-calledsteppers, in which each target portion is irradiated by exposing anentire pattern onto the target portion in one go, and so-calledscanners, in which each target portion is irradiated by scanning thepattern through the beam in a given direction (the “scanning”-direction)while synchronously scanning the substrate parallel or anti parallel tothis direction.

SUMMARY

An aspect comprises a computer-implemented defect prediction method fora device manufacturing process involving processing a portion of adesign layout onto a substrate, the method comprising: identifying a hotspot from the portion of the design layout; determining a range ofvalues of a processing parameter of the device manufacturing process forthe hot spot, wherein when the processing parameter has a value outsidethe range, a defect is produced from the hot spot with the devicemanufacturing process; determining an actual value of the processingparameter; determining or predicting, using the actual value, existence,probability of existence, a characteristic, or a combination thereof, ofa defect produced from the hot spot with the device manufacturingprocess.

In an embodiment of the method, the determining or predicting theexistence, the probability of existence, the characteristic, or thecombination thereof, further uses a characteristic of the hot spot, acharacteristic of the design layout, or both.

In an embodiment of the method, the method further comprises adjustingor compensating for the processing parameter using the existence, theprobability of existence, the characteristic, or the combinationthereof, of the defect.

In an embodiment of the method, the method further comprises carryingout reiteratively the determining or predicting the existence, theprobability of existence, the characteristic, or the combinationthereof, of the defect, and adjusting or compensating for the processingparameter.

In an embodiment of the method, the method further comprises determiningor predicting, using the adjusted or compensated processing parameter,existence, probability of existence, a characteristic, or a combinationthereof, of a residue defect produced from the hot spot using the devicemanufacturing process.

In an embodiment of the method, the method further comprises indicatingwhether the hot spot is to be inspected at least partially based on thedetermined or predicted existence, probability of existence, thecharacteristic, or the combination thereof, of the residue defect.

In an embodiment of the method, the method further comprises indicatingwhether the hot spot is to be inspected at least partially based on thedetermined or predicted existence, probability of existence, thecharacteristic, or the combination thereof, of the defect.

In an embodiment of the method, the hot spot is identified using anempirical model or a computational model.

In an embodiment of the method, the processing parameter is any one ormore selected from: actual wafer stage position and tilt, actual reticlestage position and tilt, focus, dose, a source parameter, a projectionoptics parameter, data obtained from metrology, and/or data from anoperator of a processing apparatus used in the device manufacturingprocess.

In an embodiment of the method, the processing parameter is dataobtained from metrology and the data obtained from metrology is obtainedfrom a diffractive tool, or an electron microscope.

In an embodiment of the method, the processing parameter is determinedor predicted using a model or by querying a database.

In an embodiment of the method, the determining or predicting theexistence, the probability of existence, the characteristic, or thecombination thereof, of the defect comprises simulating an image orexpected patterning contours of the hot spot under the processingparameter and determining an image or contour parameter.

In an embodiment of the method, the hot spot is identified using asensitivity of patterns of the portion, with respect to the processingparameter.

In an embodiment of the method, the method further comprises inspectingthe hot spot.

In an embodiment of the method, the method further comprises adjustingthe range of values at least partially based on inspection of the hotspot.

In an embodiment of the method, the device manufacturing processinvolves using a lithography apparatus.

In an embodiment of the method, the processing parameter is determinedimmediately before the hot spot is processed.

In an embodiment of the method, the processing parameter is selectedfrom local processing parameters or global processing parameters.

In an embodiment of the method, the identifying of the hot spot includesidentifying a location thereof.

In an embodiment of the method, the defect is undetectable before thesubstrate is irreversibly processed.

A further aspect comprises a method of manufacturing a device involvingprocessing a pattern onto a substrate or onto a die of the substrate,the method comprising: determining a processing parameter beforeprocessing the substrate or the die; predicting or determining existenceof a defect, probability of existence of a defect, a characteristic of adefect, or a combination thereof, using the processing parameter beforeprocessing the substrate or the die, and using a characteristic of thesubstrate or the die, a characteristic of the geometry of a pattern tobe processed onto the substrate or the die, or both; adjusting theprocessing parameter based on the prediction or determination so as toeliminate, reduce the probability of or reduce the severity of, thedefect.

In an embodiment of the method, the method further comprises identifyinga hot spot from the pattern.

In an embodiment of the method, the defect is a defect produced from thehot spot.

In an embodiment of the method, the characteristic of the substrate orthe die is a process window of the hot spot.

An even further aspect comprises a computer-implemented defectprediction method for a device manufacturing process involvingprocessing a portion of a design layout onto a substrate, the methodcomprising: identifying a hot spot from the portion of the designlayout; determining or predicting existence, probability of existence, acharacteristic, or a combination thereof, of a defect produced from thehot spot with the device manufacturing process; determining whether toinspect the hot spot at least partially based on the determination orprediction of the existence, probability of existence, a characteristic,or a combination thereof, of the defect.

An even further aspect comprises a computer-implemented defectprediction method for a device manufacturing process involvingprocessing a portion of a design layout onto a substrate, the methodcomprising: identifying a hot spot from the portion of the designlayout; determining a sensitivity of the hot spot with respect to aprocessing parameter of the device manufacturing process for the hotspot; generating a mark having the same sensitivity; adding the markinto the design layout.

A further aspect comprises a method of manufacturing a devicecomprising: the computer-implemented defect prediction method accordingto any of the previous embodiments; and indicating which of plurality ofhot spots to inspect at least partially based on the determined orpredicted existence, probability of existence, characteristic, or thecombination thereof, of the defect.

In an embodiment of the method, the defect is one or more selected from:necking, line pull back, line thinning, CD error, overlapping, resisttop loss, resist undercut and/or bridging.

A further aspect comprises a method of defect prediction for a devicemanufacturing process involving processing a portion of a design layoutonto a substrate, comprising: determining an actual value of aprocessing parameter of the device manufacturing process; constructingan inspection map based at least partially on the actual value, whereinthe inspection map comprises positions of potential defects on thesubstrate.

In an embodiment of the method, the method further comprises inspectingthe substrate at the positions of potential defects.

In an embodiment of the method, the method further comprises inspectingthe substrate at only the positions of potential defects.

In an embodiment of the method, the method further comprises presentingthe inspection map to a user.

A further aspect comprises a computer program product comprising acomputer readable medium having instructions recorded thereon, theinstructions when executed by a computer implementing the method of anyof the previous embodiments.

A further aspect comprises a metrology tool configured to inspect asubstrate onto which a portion of a design layout is processed by adevice manufacturing process, comprising: a data transfer unitconfigured to receive positions of potential defects on the substrate;an inspection unit configured to selectively inspect the substrate atthe positions.

In an embodiment of the metrology tool, the metrology tool is adiffractive tool or an electron microscope.

In an embodiment of the method, the inspecting of the substrate isperformed using an electron microscope or a bright-field inspectiontool.

In an embodiment of the method, the method further comprises presentingthe inspection map to a user.

In an embodiment of the method, the constructing of the inspection mapfurther comprises simulating at least some of the identified potentialdefects using a process simulation model.

In an embodiment of the method, the constructing of the inspection mapfurther comprises to construct the inspection map in a format readableby a defect inspection tool.

A further aspect comprises a metrology tool configured to inspect asubstrate onto which a portion of a design layout is processed by adevice manufacturing process, comprising: a data transfer unitconfigured to receive positions of potential defects on the substrate;an inspection unit configured to selectively inspect the substrate atthe positions.

In an embodiment of the metrology tool, the metrology tool is adiffractive tool or an electron microscope.

A further aspect comprises a metrology system for inspecting a substrateonto which a portion of a design layout is processed, the metrologysystem comprising the first metrology tool for determining an actualvalue of the processing parameter, and a defect prediction unitconfigured for executing a computer implemented method of any of theprevious embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of exampleonly, with reference to the accompanying schematic drawings in whichcorresponding reference symbols indicate corresponding parts, and inwhich:

FIG. 1 depicts a lithographic apparatus according to an embodiment ofthe invention;

FIG. 2 shows a flow chart for a method of defect prediction for a devicemanufacturing process, according to an embodiment;

FIG. 3 shows exemplary sources of the processing parameters;

FIG. 4 shows an implementation of step 214 of FIG. 2;

FIG. 5A shows an exemplary substrate with many dies;

FIG. 5B shows a usable depth of focus (uDOF) obtained using atraditional method;

FIG. 5C shows a usable depth of focus (uDOF) obtained using a methodaccording to an embodiment described herein;

FIG. 6 shows a schematic flow diagram for a processing flow;

FIG. 7 shows an exemplary map for focus;

FIG. 8 shows a flow chart for a method of defect prediction for a devicemanufacturing process involving processing a portion of a design layoutonto a substrate, according to an embodiment;

FIG. 9 shows a flow chart for a method of defect prediction for a devicemanufacturing process involving processing a portion of a design layoutonto a substrate, according to an embodiment.

DETAILED DESCRIPTION

Although specific reference may be made in this text to the use oflithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,liquid-crystal displays (LCDs), thin film magnetic heads, etc. Theskilled artisan will appreciate that, in the context of such alternativeapplications, any use of the terms “wafer” or “die” herein may beconsidered as synonymous with the more general terms “substrate” or“target portion”, respectively. The substrate referred to herein may beprocessed, before or after exposure, in for example a track (a tool thattypically applies a layer of resist to a substrate and develops theexposed resist) or a metrology or inspection tool. Where applicable, thedisclosure herein may be applied to such and other substrate processingtools. Further, the substrate may be processed more than once, forexample in order to create a multi-layer IC, so that the term substrateused herein may also refer to a substrate that already contains multipleprocessed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of 365, 248, 193, 157 or 126 nm) and extremeultra-violet (EUV) radiation (e.g. having a wavelength in the range of5-20 nm), as well as particle beams, such as ion beams or electronbeams.

The term “patterning device” used herein should be broadly interpretedas referring to a device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate. Generally, the patternimparted to the radiation beam will correspond to a particularfunctional layer in a device being created in the target portion, suchas an integrated circuit.

A patterning device may be transmissive or reflective. Examples ofpatterning device include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions; in this manner, thereflected beam is patterned.

The support structure holds the patterning device. It holds thepatterning device in a way depending on the orientation of thepatterning device, the design of the lithographic apparatus, and otherconditions, such as for example whether or not the patterning device isheld in a vacuum environment. The support can use mechanical clamping,vacuum, or other clamping techniques, for example electrostatic clampingunder vacuum conditions. The support structure may be a frame or atable, for example, which may be fixed or movable as required and whichmay ensure that the patterning device is at a desired position, forexample with respect to the projection system. Any use of the terms“reticle,” “design layout” or “mask” herein may be considered synonymouswith the more general term “patterning device”.

The term “projection system” used herein should be broadly interpretedas encompassing various types of projection system, including refractiveoptical systems, reflective optical systems, and catadioptric opticalsystems, as appropriate for example for the exposure radiation beingused, or for other factors such as the use of an immersion fluid or theuse of a vacuum. Any use of the term “projection lens” herein may beconsidered as synonymous with the more general term “projection system”.

The illumination system may also encompass various types of opticalcomponents, including refractive, reflective, and catadioptric opticalcomponents for directing, shaping, or controlling the beam of radiation,and such components may also be referred to below, collectively orsingularly, as a “lens”.

The lithographic apparatus may be of a type having two (dual stage) ormore substrate tables (and/or two or more support structures). In such“multiple stage” machines the additional tables may be used in parallel,or preparatory steps may be carried out on one or more tables while oneor more other tables are being used for exposure.

The lithographic apparatus may also be of a type wherein the substrateis immersed in a liquid having a relatively high refractive index, e.g.water, so as to fill a space between the final element of the projectionsystem and the substrate. Immersion techniques are well known in the artfor increasing the numerical aperture of projection systems.

FIG. 1 schematically depicts a lithographic apparatus according to aparticular embodiment of the invention. The apparatus comprises:

-   -   an illumination system (illuminator) IL to condition a beam B of        radiation (e.g. UV radiation or DUV radiation).    -   a support structure MT to support a patterning device (e.g. a        mask) MA and connected to first positioning device PM to        accurately position the patterning device with respect to item        PS;    -   a substrate table (e.g. a wafer table) WT for holding a        substrate (e.g. a resist coated wafer) W and connected to second        positioning device PW for accurately positioning the substrate        with respect to item PS; and    -   a projection system (e.g. a refractive projection lens) PS        configured to image a pattern imparted to the radiation beam B        by patterning device MA onto a target portion C (e.g. comprising        one or more dies) of the substrate W.

As here depicted, the apparatus is of a transmissive type (e.g.employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g. employing a programmable mirror array of a type asreferred to above).

The illuminator IL receives a beam of radiation from a radiation sourceSO. The source and the lithographic apparatus may be separate entities,for example when the source is an excimer laser. In such cases, thesource is not considered to form part of the lithographic apparatus andthe radiation beam is passed from the source SO to the illuminator ILwith the aid of a beam delivery system BD comprising for examplesuitable directing mirrors and/or a beam expander. In other cases thesource may be an integral part of the apparatus, for example when thesource is a mercury lamp. The source SO and the illuminator IL, togetherwith the beam delivery system BD if required, may be referred to as aradiation system.

The illuminator IL may alter the intensity distribution of the beam. Theilluminator may be arranged to limit the radial extent of the radiationbeam such that the intensity distribution is non-zero within an annularregion in a pupil plane of the illuminator IL. Additionally oralternatively, the illuminator IL may be operable to limit thedistribution of the beam in the pupil plane such that the intensitydistribution is non-zero in a plurality of equally spaced sectors in thepupil plane. The intensity distribution of the radiation beam in a pupilplane of the illuminator IL may be referred to as an illumination mode.

The illuminator IL may comprise adjuster AD configured to adjust theintensity distribution of the beam. Generally, at least the outer and/orinner radial extent (commonly referred to as σ-outer and σ-inner,respectively) of the intensity distribution in a pupil plane of theilluminator can be adjusted. The illuminator IL may be operable to varythe angular distribution of the beam. For example, the illuminator maybe operable to alter the number, and angular extent, of sectors in thepupil plane wherein the intensity distribution is non-zero. By adjustingthe intensity distribution of the beam in the pupil plane of theilluminator, different illumination modes may be achieved. For example,by limiting the radial and angular extent of the intensity distributionin the pupil plane of the illuminator IL, the intensity distribution mayhave a multi-pole distribution such as, for example, a dipole,quadrupole or hexapole distribution. A desired illumination mode may beobtained, e.g., by inserting an optic which provides that illuminationmode into the illuminator IL or using a spatial light modulator.

The illuminator IL may be operable alter the polarization of the beamand may be operable to adjust the polarization using adjuster AD. Thepolarization state of the radiation beam across a pupil plane of theilluminator IL may be referred to as a polarization mode. The use ofdifferent polarization modes may allow greater contrast to be achievedin the image formed on the substrate W. The radiation beam may beunpolarized. Alternatively, the illuminator may be arranged to linearlypolarize the radiation beam. The polarization direction of the radiationbeam may vary across a pupil plane of the illuminator IL. Thepolarization direction of radiation may be different in differentregions in the pupil plane of the illuminator IL. The polarization stateof the radiation may be chosen in dependence on the illumination mode.For multi-pole illumination modes, the polarization of each pole of theradiation beam may be generally perpendicular to the position vector ofthat pole in the pupil plane of the illuminator IL. For example, for adipole illumination mode, the radiation may be linearly polarized in adirection that is substantially perpendicular to a line that bisects thetwo opposing sectors of the dipole. The radiation beam may be polarizedin one of two different orthogonal directions, which may be referred toas X-polarized and Y-polarized states. For a quadrupole illuminationmode the radiation in the sector of each pole may be linearly polarizedin a direction that is substantially perpendicular to a line thatbisects that sector. This polarization mode may be referred to as XYpolarization. Similarly, for a hexapole illumination mode the radiationin the sector of each pole may be linearly polarized in a direction thatis substantially perpendicular to a line that bisects that sector. Thispolarization mode may be referred to as TE polarization.

In addition, the illuminator IL generally comprises various othercomponents, such as an integrator IN and a condenser CO. The illuminatorprovides a conditioned beam of radiation B, having a desired uniformityand intensity distribution in its cross section.

The radiation beam B is incident on the patterning device (e.g. mask)MA, which is held on the support structure MT. Having traversed thepatterning device MA, the beam B passes through the lens PS whichfocuses the beam onto a target portion C of the substrate W. With theaid of the second positioning device PW and position sensor IF (e.g. aninterferometric device), the substrate table WT can be moved accurately,e.g. so as to position different target portions C in the path of thebeam B. Similarly, the first positioning device PM and another positionsensor (which is not explicitly depicted in FIG. 1) can be used toaccurately position the patterning device MA with respect to the path ofthe beam B, e.g. after mechanical retrieval from a mask library, orduring a scan. In general, movement of the object tables MT and WT willbe realized with the aid of a long-stroke module (coarse positioning)and a short-stroke module (fine positioning), which form part of thepositioning device PM and PW. However, in the case of a stepper (asopposed to a scanner) the support structure MT may be connected to ashort stroke actuator only, or may be fixed. Patterning device MA andsubstrate W may be aligned using patterning device alignment marks M1,M2 and substrate alignment marks P1, P2.

The depicted apparatus can be used in the following preferred modes:

1. In step mode, the support structure MT and the substrate table WT arekept essentially stationary, while an entire pattern imparted to thebeam B is projected onto a target portion C in one go (i.e. a singlestatic exposure). The substrate table WT is then shifted in the X and/orY direction so that a different target portion C can be exposed. In stepmode, the maximum size of the exposure field limits the size of thetarget portion C imaged in a single static exposure.2. In scan mode, the support structure MT and the substrate table WT arescanned synchronously while a pattern imparted to the beam B isprojected onto a target portion C (i.e. a single dynamic exposure). Thevelocity and direction of the substrate table WT relative to the supportstructure MT is determined by the (de-)magnification and image reversalcharacteristics of the projection system PS. In scan mode, the maximumsize of the exposure field limits the width (in the non-scanningdirection) of the target portion in a single dynamic exposure, whereasthe length of the scanning motion determines the height (in the scanningdirection) of the target portion.3. In another mode, the support structure MT is kept essentiallystationary holding a programmable patterning device, and the substratetable WT is moved or scanned while a pattern imparted to the beam B isprojected onto a target portion C. In this mode, generally a pulsedradiation source is employed and the programmable patterning device isupdated as required after each movement of the substrate table WT or inbetween successive radiation pulses during a scan. This mode ofoperation can be readily applied to maskless lithography that utilizesprogrammable patterning device, such as a programmable mirror array of atype as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

The projection system PS has an optical transfer function which may benon-uniform, which can affect the pattern imaged on the substrate W. Forunpolarized radiation such effects can be fairly well described by twoscalar maps, which describe the transmission (apodization) and relativephase (aberration) of radiation exiting the projection system PS as afunction of position in a pupil plane thereof. These scalar maps, whichmay be referred to as the transmission map and the relative phase map,may be expressed as a linear combination of a complete set of basisfunctions. A particularly convenient set is the Zernike polynomials,which form a set of orthogonal polynomials defined on a unit circle. Adetermination of each scalar map may involve determining thecoefficients in such an expansion. Since the Zernike polynomials areorthogonal on the unit circle, the Zernike coefficients may bedetermined by calculating the inner product of a measured scalar mapwith each Zernike polynomial in turn and dividing this by the square ofthe norm of that Zernike polynomial.

The transmission map and the relative phase map are field and systemdependent. That is, in general, each projection system PS will have adifferent Zernike expansion for each field point (i.e. for each spatiallocation in its image plane). The relative phase of the projectionsystem PS in its pupil plane may be determined by projecting radiation,for example from a point-like source in an object plane of theprojection system PS (i.e. the plane of the patterning device MA),through the projection system PS and using a shearing interferometer tomeasure a wavefront (i.e. a locus of points with the same phase). Ashearing interferometer is a common path interferometer and therefore,advantageously, no secondary reference beam is required to measure thewavefront. The shearing interferometer may comprise a diffractiongrating, for example a two dimensional grid, in an image plane of theprojection system (i.e. the substrate table WT) and a detector arrangedto detect an interference pattern in a plane that is conjugate to apupil plane of the projection system PS. The interference pattern isrelated to the derivative of the phase of the radiation with respect toa coordinate in the pupil plane in the shearing direction. The detectormay comprise an array of sensing elements such as, for example, chargecoupled devices (CCDs).

The diffraction grating may be sequentially scanned in two perpendiculardirections, which may coincide with axes of a co-ordinate system of theprojection system PS (x and y) or may be at an angle such as 45 degreesto these axes. Scanning may be performed over an integer number ofgrating periods, for example one grating period. The scanning averagesout phase variation in one direction, allowing phase variation in theother direction to be reconstructed. This allows the wavefront to bedetermined as a function of both directions.

The projection system PS of a state of the art lithographic apparatusmay not produce visible fringes and therefore the accuracy of thedetermination of the wavefront can be enhanced using phase steppingtechniques such as, for example, moving the diffraction grating.Stepping may be performed in the plane of the diffraction grating and ina direction perpendicular to the scanning direction of the measurement.The stepping range may be one grating period, and at least three(uniformly distributed) phase steps may be used. Thus, for example,three scanning measurements may be performed in the y-direction, eachscanning measurement being performed for a different position in thex-direction. This stepping of the diffraction grating effectivelytransforms phase variations into intensity variations, allowing phaseinformation to be determined. The grating may be stepped in a directionperpendicular to the diffraction grating (z direction) to calibrate thedetector.

The transmission (apodization) of the projection system PS in its pupilplane may be determined by projecting radiation, for example from apoint-like source in an object plane of the projection system PS (i.e.the plane of the patterning device MA), through the projection system PSand measuring the intensity of radiation in a plane that is conjugate toa pupil plane of the projection system PS, using a detector. The samedetector as is used to measure the wavefront to determine aberrationsmay be used. The projection system PS may comprise a plurality ofoptical (e.g., lens) elements and may further comprise an adjustmentmechanism PA configured to adjust one or more of the optical elements soas to correct for aberrations (phase variations across the pupil planethroughout the field). To achieve this, the adjustment mechanism PA maybe operable to manipulate one or more optical (e.g., lens) elementswithin the projection system PS in one or more different ways. Theprojection system may have a co-ordinate system wherein its optical axisextends in the z direction. The adjustment mechanism PA may be operableto do any combination of the following: displace one or more opticalelements; tilt one or more optical elements; and/or deform one or moreoptical elements. Displacement of optical elements may be in anydirection (x, y, z or a combination thereof). Tilting of opticalelements is typically out of a plane perpendicular to the optical axis,by rotating about axes in the x or y directions although a rotationabout the z axis may be used for non-rotationally symmetric asphericaloptical elements. Deformation of optical elements may include both lowfrequency shapes (e.g. astigmatic) and high frequency shapes (e.g. freeform aspheres). Deformation of an optical element may be performed forexample by using one or more actuators to exert force on one or moresides of the optical element and/or by using one or more heatingelements to heat one or more selected regions of the optical element. Ingeneral, it may not be possible to adjust the projection system PS tocorrect for apodizations (transmission variation across the pupilplane). The transmission map of a projection system PS may be used whendesigning a patterning device (e.g., mask) MA for the lithographicapparatus. Using a computational lithography technique, the patterningdevice MA may be designed to at least partially correct forapodizations.

A space of processing parameters under which a pattern will be producedwithin specifications may be referred to as a process window for thatpattern. If a pattern is produced out of specifications, it is a defect.The patterns on a patterning device may be affected differently byvariations of the processing parameters. For example, a pattern may bemore sensitive to variations of the dose than another pattern.Therefore, the patterns on a patterning device may have differentprocess windows. The sensitivity of a pattern with respect to aprocessing parameter may, for example, be measured by a partialderivative of a characteristic of the pattern with respect to theprocessing parameter. Examples of pattern specifications that relate topotential systematic defects include checks for necking, line pull back,line thinning, CD, edge placement, overlapping, resist top loss, resistundercut and bridging. The process window of all the patterns on apatterning device may be obtained by merging (e.g., overlapping) processwindows of each individual pattern. The boundary of the process windowof all the patterns contains boundaries of process windows of some ofthe individual patterns. In other words, these individual patterns limitthe process window of all the patterns. These patterns can be referredto as “hot spots” or “process window limiting patterns (PWLPs),” whichare used interchangeably herein. When controlling a lithography process,it is possible and economical to focus on the hot spots. When the hotspots are not defective, it is most likely that all the patterns are notdefective.

Processing parameters may vary with position on a substrate and withtime (e.g., between substrates, between dies). Such variation may becaused by change in the environment such as temperature and humidity.Other causes of such variations may include drift in one or morecomponents in the processing apparatus such as the source, projectionoptics, substrate table, height variations of substrate surfaces, etc.in a lithography apparatus. It would be useful to be aware of suchvariations and their effects on PWLPs or potential patterning defects,and to adjust the lithography process to accommodate such variations soas to reduce actual defects. To reduce the computational cost oftracking these variations, one can choose to monitor only the hot spots.

FIG. 2 shows a flow chart for a method of defect prediction for a devicemanufacturing process, according to an embodiment. In step 211, at leasta hot spot is identified using any suitable method from a portion of adesign layout. For example, the hot spot may be identified by analyzingpatterns in the portion of the design layout using an empirical model ora computational model. In an empirical model, images (e.g., resistimage, optical image, etch image) of the patterns are not simulated;instead, the empirical model predicts defects or probability of defectsbased on correlations between processing parameters, parameters of thepatterns, and the defects. For example, an empirical model may be aclassification model or a database of patterns prone to defects. In acomputational model, a portion or a characteristic of the images iscalculated or simulated, and defects are identified based on the portionor the characteristic. For example, a line pull back defect may beidentified by finding a line end too far away from its desired location;a bridging defect may be identified by finding a location where twolines undesirably join; an overlapping defect may be identified byfinding two features on separate layers undesirably overlap orundesirably not overlap. An empirical model is usually lesscomputationally expensive than a computational model. In an example, thehot spots and/or their locations may be determined experimentally, suchas by FEM wafer inspection or a suitable metrology tool.

In an embodiment, the hot spot may be identified using the sensitivityof the patterns with respect to a processing parameter. For example, ifthe sensitivity of a pattern is greater than a threshold, that patternmay be identified as a hot spot.

The defects may include those defects that cannot be detected in anafter-development-inspection (ADI) (usually optical inspection), such asresist top loss, resist undercut, etc. Conventional inspection onlyreveals such defects after the substrate is irreversibly processed(e.g., etched), at which point the wafer cannot be reworked. So, suchresist top loss defects cannot be detected using the current opticaltechnology at the time of drafting this document. However, simulationmay be used to determine where resist top loss may occur and what theseverity would be. Based on this information, it may be either decidedto inspect the specific possible defect using a more accurate inspectionmethod (and typically more time consuming) to determine whether thedefect needs rework, or it may be decided to rework the imaging of thespecific resist layer (remove the resist layer having the resist toploss defect and recoat the wafer to redo the imaging of the specificlayer) before the irreversible processing (e.g., etching) is done.

In step 212, a range of values of a processing parameter of the devicemanufacturing process is determined for the hot spot, where the devicemanufacturing process produces a defect from the hot spot when theprocessing parameter has a value outside the range. Multiple ranges ofvalues for multiple processing parameters may also be determined for thehot spot. The one or more ranges determined may be compiled as a processwindow of the hot spot. It is possible to determine and/or compileprocess windows of multiple hot spots into a map, based on hot spotlocations and process windows of individual hot spots—i.e. determineprocess windows as a function of hot spot locations. This process windowmap may characterize the layout-specific sensitivities and processingmargins of the patterns. The processing parameters may belocal—dependent on the locations of the hot spots, the dies, or both.The processing parameters may be global—independent of the locations ofthe hot spots and the dies.

In step 213, an actual value of the processing parameter is determined.During a lithographic process the pattern may be produced using specificsettings of the processing parameters which, for example, may be chosento ensure that the pattern will be processed within the process window.However, the actual processing parameter at which the pattern isproduced may be different from the set parameter, for example, due todrift of the lithographic process, or, for example, due to globally setprocessing parameters which may locally deviate. One such localdeviation of a globally set processing parameter may, for example, be afocus position, which may globally be at the set processing parameter,but which locally may differ due to, for example, a tilt of thesubstrate during the lithographic process. So for a specific hot spot,the actual value of the processing parameter may vary from a setprocessing parameter. One exemplary way to determine the actual value ofthe processing parameter is to determine the status of the lithographicapparatus. For example, actual wafer stage position and tilt may be usedto calculate the local actual value of the processing parameter. Butalso actual reticle stage position and tilt, laser bandwidth, focus,dose, source parameters, projection optics parameters, and the spatialor temporal variations of these parameters, may be measured directlyfrom the lithographic apparatus and used to determine the actual valueof the processing parameter. Another exemplary way is to infer theprocessing parameters from data obtained from metrology performed on thesubstrate. This metrology is performed on an already exposed substrateand may, for example, be used to identify machine drift. Alternatively,the actual value of the processing parameter may be obtained from anoperator of the processing apparatus. For example, metrology may includeinspecting a substrate using a diffractive tool (e.g., ASML YieldStar,or a diffraction phase microscopy), an electron microscope, or othersuitable inspection tools. It is possible to obtain processingparameters for any location on a processed substrate, including theidentified hot spots. The processing parameters may be compiled into amap—lithographic parameters, or process conditions, as a function oflocation. FIG. 7 shows an exemplary map for focus. Of course, otherprocessing parameters may be represented as functions of location, i.e.,a map. In an embodiment, the processing parameters may be determinedbefore, and preferably immediately before or even during processing eachhot spot.

In step 214, existence, probability of existence, characteristics, or acombination thereof, of a defect produced from the hot spot isdetermined using the actual value of the processing parameter. Thisdetermination or prediction may be simply by comparing the actual valueof the processing parameter with the range of values thereof determinedin step 212—if the actual value falls within the range, no defect willbe expected to exist; if the actual value falls outside the range, atleast one defect will be expected to exist. This determination orprediction may also be done using a suitable empirical model (includinga statistical model). For example, a classification model may be used toprovide a probability of existence of a defect. Another way to make thisdetermination is to use a computational model to simulate an image orexpected patterning contours of the hot spot under the actual value anddetermining the expected image or contour parameters from suchsimulation. The determined existence and/or characteristics of a defectmay serve as a basis for a decision of disposition: rework, detailedinspection using, for example, an inspection tool such as an electronmicroscope, or acceptance of the possible defect. In an embodiment, theactual value is a moving average of the processing parameter. Movingaverages are useful to capture long term drifts of the processingparameter, without distraction by short term fluctuations.

In optional step 215, the processing parameter may be adjusted orcompensated for using the existence, probability of existence,characteristics, or a combination thereof as determined in step 214(i.e., the prediction or determination is fed back to adjust theprocessing parameter), so that the defect is eliminated or its severityreduced. This process may, for example, be used to continuously monitordrift in the lithographic process and reduce this drift. In afeed-forward example, if the hot spot to be imaged would be located on abump of a substrate, thereby causing the actual value of the focus tofall outside a range of value for the focus, the focus or levelling ofthe die may be adjusted to fall into the range before imaging the hotspot onto the substrate, thereby eliminating or strongly reducing thedefect on that hot spot. In this example, if adjusting the focus isundesirable (e.g., due to limitation of hardware, or side effect of suchadjustment), it may be compensated for by adjusting other parameters,thereby changing the range of the overall processing parameters suchthat the actual value of the focus falls within an acceptable range.Preferably, the processing parameter is adjusted or compensated forimmediately before processing the hot spot. Steps 214 and 215 may bereiterative. The processing parameter may also be adjusted orcompensated for after processing of one or multiple substrates,especially when an average (e.g., a moving average) of the processingparameter is determined, in order to accommodate systematic or slowlyvarying process variations, or to address a larger number of adjustableprocessing parameters. Adjustment or compensation of the processingparameter may include adjustment to wafer stage position and tilt,reticle stage position and tilt, focus, dose, source or pupil phase.

In optional step 216, existence and/or characteristics of a residuedefect may be determined using the adjusted processing parameter. Aresidue defect is a defect that cannot be eliminated by adjusting theprocessing parameter. This determination may be simply comparing theadjusted processing parameter and the range—if the adjusted processingparameter falls within the range, no residue defect is expected toexist; if the adjusted processing parameter falls outside the range, atleast one residue defect will be expected to exist. This determinationmay also be done using a suitable empirical model (including astatistical model). For example, a classification model may be used toprovide a probability of existence of a residue defect. Another way tomake this determination is to use a computational model to simulate animage or expected patterning contours of the hot spot under the adjustedprocessing parameters and determine the expected image or contourparameters from such simulation. The determined existence and/orcharacteristics of a residue defect may serve as a basis for a decisionof disposition: rework, detailed inspection using, for example, aninspection tool, or acceptance.

In optional step 217, an indication of which hot spots are subject toinspection may be made at least partially based on the determined orpredicted existence, probability of existence, one or morecharacteristics, or a combination thereof, of the residue defect or thedefect. For example, if a substrate has a probability of having one ormore residue defects or defects, the substrate may be subject tosubstrate inspection. The prediction or determination of residue defectsor defects feeds forward to inspection. These hot spots may be actuallyinspected using a suitable inspection tool to confirm whether a defectis actually present, which makes it possible to avoid inspecting allpatterns in the portion of the design layout. In the known lithographicprocess flow, an initial bright-field inspection is performed (typically“die-to-die” or “die-to-database”) substantially on the whole substrateto get an initial indication where possible defects may be located onthe substrate. This is a relatively time consuming process in whichpossible defects may be identified at random. The currently knownbright-field inspection tools capture a relatively low resolution imagefrom which only an indication of a possible defect can be obtained(often via the interpretation of the image by an experience operator).The identified locations of these possible defects as identified by thebright-field inspection tool will typically be further inspected using adetailed inspection tool, such as an electron microscope. Using thecomputer-implemented defect prediction tool according to the disclosuremay replace at least a part of the bright-field inspection step. Usingthe actual value of the processing parameter present during themanufacturing process allows to predict—without using these bright-fieldinspections—where defects may be expected and what locations thedetailed inspection tool should further investigate or shouldacknowledge the existence of the defect. Furthermore, the use of thecomputer implemented defect prediction tool according to the disclosureenables to actively look for defects, guided by the local actual valuesof the processing parameters. This use of the defect prediction tool maymake the process of finding possible defects less random. In analternative process flow, the computer-implemented defect predictiontool may be used to guide the bright-field inspection tools toinvestigate only part of the substrate—thereby allowing significantreduction of the overall inspection time at the bright-field inspectiontools and making the overall defect inspection by the bright-field toolsless random. The result of the inspection may be used to decide what todo with the pattern from the currently used lithographic process step:accept the current process step, or, if possible and necessary, reworkthe current lithographic process step. Such rework may, for example,include the stripping of the defective resist layer and re-applying anew resist layer and repeating the lithographic process step. The resultof the inspection may also be used to adjust the range of values of theprocessing parameter of the device manufacturing process used todetermine whether a hot spot may become a defect when processed at aprocessing parameter having a value outside the range. This adjustmentof the range of values may make the defect determination or predictionmore accurate. It is also possible to adjust the stringency ofinspection by increasing or decreasing the range in step 212 before step214. Decreasing the range causes more findings of a defect and possiblymore false positives.

FIG. 3 shows exemplary sources of the processing parameter 350. Onesource may be data 310 of the processing apparatus, such as parametersof the source, projection optics, substrate stage, etc. of a lithographyapparatus. Another source may be data 320 from various substratemetrology tools, such as wafer height map, focus map, CDU map, overlaymap etc. Data 320 may be obtained before substrates are subject to astep (e.g., etch) that prevents reworking of the substrate. Anothersource may be data 330 from various patterning device metrology tools,mask CDU map, mask film stack parameters variation, etc. Yet anothersource may be data 340 from an operator of the processing apparatus.

FIG. 4 shows an exemplary implementation of step 214 of FIG. 2. Theprocessing parameter 420 may be used as input (e.g., independentvariables) to a classification model 430. The processing parameter 420may include a characteristic of the source (e.g., intensity, pupilprofile, etc.), a characteristic of the projection optics, dose, focus,characteristics of the resist, a characteristic of development andpost-exposure baking of the resist, or a characteristic of etching,actual wafer stage position and tilt, actual reticle stage position andtilt. The term “classifier” or “classification model” sometimes alsorefers to the mathematical function, implemented by a classificationalgorithm, that maps input data to a category. In machine learning andstatistics, classification is the problem of identifying to which of aset of categories 440 (sub-populations) a new observation belongs, onthe basis of a training set of data containing observations (orinstances) whose category membership is known. The individualobservations are analyzed into a set of quantifiable properties, knownas various explanatory variables, features, etc. These properties mayvariously be categorical (e.g. “good”—a lithographic process that doesnot produce defects or “bad”—a lithographic process that producesdefects; “type 1”, “type 2”, . . . “type n”—different types of defects).Classification is considered an instance of supervised learning, i.e.learning where a training set of correctly identified observations isavailable. Examples of classification models are, logistic regressionand multinomial logit, probit regression, the perceptron algorithm,support vector machines, import vector machines, and linear discriminantanalysis.

One example of the processing parameters is substrate levelling. FIG. 5Ashows an exemplary substrate with many dies (depicted as grids). In adie called out, hot spots (depicted as circles) are identified alongwith less critical positions (i.e., positions that are not processwindow limiting, depicted as diamonds) in the patterns in the die. FIG.5B shows a usable depth of focus (uDOF) obtained using a traditionalmethod. uDOF is the depth of focus that falls within the process windowsof all the patterns in an exposure slit. FIG. 5C shows a usable depth offocus (uDOF) obtained using a method according to an embodimentdescribed herein, where less critical positions regions (diamonds) areallowed to drift farther away from their respective best focuses tobring the best focuses of the hot spots (circles) closer by adjustingthe processing parameters including the substrate levelling, therebyincreasing the uDOF. According to an embodiment, a method describedherein allows adjustment of processing parameters for each substrate oreven each die or even at specific locations within a die. FIG. 6 shows aschematic flow diagram for a processing flow. In step 610, processingparameters immediately (e.g., after processing the immediately previoussubstrate or die) before processing a substrate or a die are determined.In step 620, a prediction or determination of the existence of a defect,probability of existence of a defect, a characteristic of a defect, or acombination thereof is made using the processing parameters immediatelybefore processing the substrate or the die, and using a characteristicof the substrate or the die (e.g., as determined from metrology on thesubstrate or the die) and/or a characteristic of the geometry ofpatterns to be processed onto the substrate or the die. In step 630, theprocessing parameters are adjusted based on the prediction so as toeliminate, reduce the probability or severity of the defect.Alternatively, it may be known from simulations of the layout to beprocessed that the PWLP may be located at a specific area within a die.In such a situation, the system in the imaging tool which ensures theleveling of the die before exposure in the imaging tool may ensure thatthis specific area is in focus allowing other areas of the die to divertfurther from focus to ensure that the PWLP are imaged in spec. Thesimulations may further be used to determine whether the less criticalstructures are still imaged correctly due to the less favorableprocessing conditions because of the preferred leveling accuracy of thearea containing the PWLPs. According to an embodiment, a methoddescribed herein allows inspection of fewer substrates among aproduction batch while maintaining comparable defect rates to that in aconventional processing flow. A conventional processing flow involvesprocessing (e.g., exposing in a lithography apparatus) a batch ofsubstrates, 2%-3% or more of the batch has to be inspected in order tocatch most of the defects. Inspection is usually destructive. Therefore,2%-3% or more of the batch is wasted and adds to the cost of processing.The method described herein allows a processing flow in which less than2%, less than 1.5%, or less than 1% of a batch of substrates to beinspected without adverse effects such as increase defect rates.Specifically, the method described herein enables a method ofmanufacturing a device involving processing patterns onto a batch ofsubstrates, e.g., using a lithography apparatus, the method including:processing the batch of substrates, destructively inspecting less than2%, less than 1.5%, or less than 1% of the batch to determine existenceof defects in the patterns processed onto the substrates.

FIG. 8 shows a flow chart for a method of defect prediction for a devicemanufacturing process involving processing a portion of a design layoutonto a substrate, according to an embodiment. In step 811, a hot spot isidentified from the portion of the design layout. The hot spot may beidentified using any suitable method such as those described above. Instep 812, a sensitivity of the hot spot with respect to a processingparameter of the device manufacturing process is determined. One way todetermine the sensitivity is simply by deducing a partial derivative ofa characteristic of the hot spot with respect to the processingparameter, from a model that simulates the characteristic at leastpartially based on the processing parameter. Another way is simulating acharacteristic of the hot spot under at least two values of theprocessing parameter. In step 813, a mark with the same or similarsensitivity is generated or a mark with the same or (most) similarsensitivity is selected from a pool of marks designed for a specificlithography tool or a specific metrology tool. The mark may be ascatterometry target suitable for ADI or after-development-inspection(AEI). A scatterometry target may include arrays of uniformlyconstructed and uniformly spaced periodic features (for example an arrayof 100 nm diameter dots). In step 814, the designed or selected mark isadded into the design layout and processed in the same way as the designlayout on the substrate. For example, the mark may be added into thedies—integrated into the design layout, between the dies—added to theso-called scribe lanes on a substrate, or at the edge of the substrateor otherwise in between dies. The mark may be inspected in lieu of or inaddition to the hot spot. More information of generating or selectingthe mark may be found in commonly-assigned U.S. patent application Ser.Nos. 13/542,625, 61/921,874, 61/921,907, 61/921,939, 61/921,817, each ofwhich is hereby incorporated by reference in its entirety.

FIG. 9 shows a flow chart for a method of defect prediction for a devicemanufacturing process involving processing a portion of a design layoutonto a substrate, according to an embodiment. In step 911, an actualvalue of a processing parameter of the device manufacturing process isdetermined. One exemplary way to determine the processing parameter isto determine the status of the lithographic apparatus. For example,actual wafer stage position and tilt, actual reticle stage position andtilt, laser bandwidth, focus, dose, source parameters, projection opticsparameters, and the spatial or temporal variations of these parameters,may be measured from the lithographic apparatus. Another exemplary wayis to infer the processing parameters from data obtained from metrologyperformed on the substrate, or from operator of the processingapparatus. For example, metrology may include inspecting a substrateusing a diffractive tool (e.g., ASML YieldStar), an electron microscope,or other suitable inspection tools. It is possible to obtain processingparameters for any location on a processed substrate, including theidentified hot spots. In step 912, an inspection map is constructedbased at least partially on the actual value. The inspection mapincludes positions of potential defects on the substrate. The potentialdefects may be identified by comparing the actual value with aposition-dependent range, where if the actual value falls outside therange at a position, a potential defect exists at that position. In step913, the substrate is inspected at the positions of potential defects.In an embodiment, the substrate is inspected at only the positions ofpotential defects. Alternatively, in step 914, the inspection map ispresented to a user.

According to an embodiment, a metrology tool configured to inspect asubstrate may be configured to receive positions of potential defectsfrom any of the methods described above. For example, the metrology toolmay be a diffractive tool, a bright-field inspection tool or an electronmicroscope.

The invention may further be described using the following clauses:

1. A computer-implemented defect prediction method for a devicemanufacturing process involving processing a portion of a design layoutonto a substrate, the method comprising:

-   -   identifying a hot spot from the portion of the design layout;    -   determining a range of values of a processing parameter of the        device manufacturing process for the hot spot, wherein when the        processing parameter has a value outside the range, a defect is        produced from the hot spot with the device manufacturing        process;    -   determining an actual value of the processing parameter;    -   determining or predicting, using the actual value, existence,        probability of existence, a characteristic, or a combination        thereof, of a defect produced from the hot spot with the device        manufacturing process.        2. The method of clause 1, wherein the determining or predicting        the existence, the probability of existence, the characteristic,        or the combination thereof, further uses a characteristic of the        hot spot, a characteristic of the design layout, or both        3. The method of clause 1 or clause 2, further comprising        adjusting or compensating for the processing parameter using the        existence, the probability of existence, the characteristic, or        the combination thereof, of the defect.        4. The method of clause 3, further comprising carrying out        reiteratively the determining or predicting the existence, the        probability of existence, the characteristic, or the combination        thereof, of the defect, and adjusting or compensating for the        processing parameter.        5. The method of clause 3 or clause 4, further comprising        determining or predicting, using the adjusted or compensated        processing parameter, existence, probability of existence, a        characteristic, or a combination thereof, of a residue defect        produced from the hot spot using the device manufacturing        process.        6. The method of clause 5, further comprising indicating whether        the hot spot is to be inspected at least partially based on the        determined or predicted existence, probability of existence, the        characteristic, or the combination thereof, of the residue        defect.        7. The method of any of clauses 1 to 4, further comprising        indicating whether the hot spot is to be inspected at least        partially based on the determined or predicted existence,        probability of existence, the characteristic, or the combination        thereof, of the defect.        8. The method of any of clauses 1 to 7, wherein the hot spot is        identified using an empirical model or a computational model.        9. The method of any of clauses 1 to 8, wherein the processing        parameter is any one or more selected from: actual wafer stage        position and tilt, actual reticle stage position and tilt,        focus, dose, a source parameter, a projection optics parameter,        data obtained from metrology, and/or data from an operator of a        processing apparatus used in the device manufacturing process.        10. The method of clause 9, wherein the processing parameter is        data obtained from metrology and the data obtained from        metrology is obtained from a diffractive tool, or an electron        microscope.        11. The method of any of clauses 1 to 10, wherein the processing        parameter is determined or predicted using a model or by        querying a database.        12. The method of any of clauses 1 to 11, wherein the        determining or predicting the existence, the probability of        existence, the characteristic, or the combination thereof, of        the defect comprises simulating an image or expected patterning        contours of the hot spot under the processing parameter and        determining an image or contour parameter.        13. The method of clause 8, wherein the hot spot is identified        using a sensitivity of patterns of the portion, with respect to        the processing parameter.        14. The method of any of clauses 6 to 7, further comprising        inspecting the hot spot.        15. The method of clause 14, further comprising adjusting the        range of values at least partially based on inspection of the        hot spot.        16. The method of any of clauses 1 to 15, wherein the device        manufacturing process involves using a lithography apparatus.        17. The method of any of clauses 1 to 16, wherein the processing        parameter is determined immediately before the hot spot is        processed.        18. The method of any of clauses 1 to 17, wherein the processing        parameter is selected from local processing parameters or global        processing parameters.        19. The method of any of clauses 1 to 18, wherein identifying        the hot spot includes identifying a location thereof.        20. The method of any of clauses 1 to 19, wherein the defect is        undetectable before the substrate is irreversibly processed.        21. A method of manufacturing a device involving processing a        pattern onto a substrate or onto a die of the substrate, the        method comprising:    -   determining a processing parameter before processing the        substrate or the die;    -   predicting or determining existence of a defect, probability of        existence of a defect, a characteristic of a defect, or a        combination thereof, using the processing parameter before        processing the substrate or the die, and using a characteristic        of the substrate or the die, a characteristic of the geometry of        a pattern to be processed onto the substrate or the die, or        both;    -   adjusting the processing parameter based on the prediction or        determination so as to eliminate, reduce the probability of or        reduce the severity of, the defect.        22. The method of clause 21, further comprising identifying a        hot spot from the pattern.        23. The method of clause 21, wherein the defect is a defect        produced from the hot spot.        24. The method of clause 21, wherein the characteristic of the        substrate or the die is a process window of the hot spot.        25. A computer-implemented defect prediction method for a device        manufacturing process involving processing a portion of a design        layout onto a substrate, the method comprising:    -   identifying a hot spot from the portion of the design layout;    -   determining or predicting existence, probability of existence, a        characteristic, or a combination thereof, of a defect produced        from the hot spot with the device manufacturing process;    -   determining whether to inspect the hot spot at least partially        based on the determination or prediction of the existence,        probability of existence, a characteristic, or a combination        thereof, of the defect.        26. A computer-implemented defect prediction method for a device        manufacturing process involving processing a portion of a design        layout onto a substrate, the method comprising:    -   identifying a hot spot from the portion of the design layout;    -   determining a sensitivity of the hot spot with respect to a        processing parameter of the device manufacturing process for the        hot spot;    -   generating a mark having the same sensitivity;    -   adding the mark into the design layout.        27. A method of manufacturing a device comprising: the        computer-implemented defect prediction method according to any        of clauses 1 to 26; and    -   indicating which of plurality of hot spots to inspect at least        partially based on the determined or predicted existence,        probability of existence, characteristic, or the combination        thereof, of the defect.        28. The method of any of clauses 1 to 27, wherein the defect is        one or more selected from: necking, line pull back, line        thinning, CD error, overlapping, resist top loss, resist        undercut and/or bridging.        29. A method of defect prediction for a device manufacturing        process involving processing a portion of a design layout onto a        substrate, comprising:    -   determining an actual value of a processing parameter of the        device manufacturing process;    -   constructing an inspection map based at least partially on the        actual value, wherein the inspection map comprises positions of        potential defects on the substrate.        30. The method of clause 29, further comprising inspecting the        substrate at the positions of potential defects.        31. The method of clause 29, further comprising inspecting the        substrate at only the positions of potential defects.        32. The method of clause 30 or 31, wherein inspecting the        substrate is performed using an electron microscope or a        bright-field inspection tool.        33. The method of clause 29, further comprising presenting the        inspection map to a user.        34. The method of clause 29, wherein constructing the inspection        map further comprises simulating at least some of the identified        potential defects using a process simulation model.        35. The method of clause 29 or 34, wherein constructing the        inspection map further comprises to construct the inspection map        in a format readable by a defect inspection tool.        36. A computer program product comprising a computer readable        medium having instructions recorded thereon, the instructions        when executed by a computer implementing the method of any of        clauses 1 to 35.        37. A metrology tool configured to inspect a substrate onto        which a portion of a design layout is processed by a device        manufacturing process, comprising:    -   a data transfer unit configured to receive positions of        potential defects on the substrate;    -   an inspection unit configured to selectively inspect the        substrate at the positions.        38. The metrology tool of clause 37, wherein the metrology tool        is a diffractive tool or an electron microscope.        39. A metrology system for inspecting a substrate onto which a        portion of a design layout is processed, the metrology system        comprising the first metrology tool for determining an actual        value of the processing parameter, and a defect prediction unit        configured for executing a computer implemented method of any of        the clauses 1 to 35.        40. The metrology system according to clause 39, wherein the        metrology system further comprises a second metrology tool being        the metrology tool as claimed in any of the clauses 37 and 38.

Embodiments of the invention may be implemented in hardware, firmware,software, or any combination thereof. Embodiments of the invention mayalso be implemented as instructions stored on a machine-readable medium,which may be read and executed by one or more processors. Amachine-readable medium may include any mechanism for storing ortransmitting information in a form readable by a machine (e.g., acomputing device). For example, a machine-readable medium may includeread only memory (ROM); random access memory (RAM); magnetic diskstorage media; optical storage media; flash memory devices; electrical,optical, acoustical or other forms of propagated signals (e.g. carrierwaves, infrared signals, digital signals, etc.), and others. Further,firmware, software, routines, instructions may be described herein asperforming certain actions. However, it should be appreciated that suchdescriptions are merely for convenience and that such actions in factresult from computing devices, processors, controllers, or other devicesexecuting the firmware, software, routines, instructions, etc.

While specific embodiments of the invention have been described above,it will be appreciated that the invention may be practiced otherwisethan as described. The description is not intended to limit theinvention.

1. A non-transitory computer readable medium having instructionsrecorded thereon, the instructions, when executed by a computer,configured to: identify a hot spot from a portion of a design layout tobe processed onto a substrate by a device manufacturing process;determine a range of values of a processing parameter of the devicemanufacturing process for the hot spot, wherein when the processingparameter has a value outside the range, a defect is produced from thehot spot using the device manufacturing process; determine an actualvalue of the processing parameter; and determine or predict, using theactual value and by a computer hardware system, an existence, aprobability of existence, a characteristic, or a combination selectedtherefrom, of a defect produced from the hot spot using the devicemanufacturing process.
 2. The computer readable medium of claim 1,wherein the instructions configured to determine or predict anexistence, a probability of existence, a characteristic, or acombination selected therefrom, of a defect are further configured touse a characteristic of the hot spot, a characteristic of the designlayout, or both, to determine or predict an existence, a probability ofexistence, a characteristic, or a combination selected therefrom, of adefect.
 3. The computer readable medium of claim 1, wherein theinstructions are further configured to adjust, or compensate for, theprocessing parameter using the existence, the probability of existence,the characteristic, or the combination selected therefrom, of thedefect.
 4. The computer readable medium of claim 3, wherein theinstructions are further configured to determine or predict, using theadjustment of, or compensation for, the processing parameter, anexistence, a probability of existence, a characteristic, or acombination selected therefrom, of a residue defect produced from thehot spot using the device manufacturing process.
 5. The computerreadable medium of claim 4, wherein the instructions are furtherconfigured to indicate whether the hot spot is to be inspected at leastpartially based on the determined or predicted existence, probability ofexistence, the characteristic, or the combination selected therefrom, ofthe residue defect.
 6. The computer readable medium of claim 5, whereinthe instructions are further configured to cause inspection of the hotspot as produced on the substrate using the device manufacturingprocess.
 7. The computer readable medium of claim 1, wherein theinstructions are further configured to indicate whether the hot spot isto be inspected at least partially based on the determined or predictedexistence, probability of existence, characteristic, or combinationselected therefrom, of the defect produced from the hot spot using thedevice manufacturing process.
 8. The computer readable medium of claim7, wherein the instructions are further configured to cause inspectionof the hot spot as produced on the substrate using the devicemanufacturing process.
 9. The computer readable medium of claim 1,wherein the hot spot is identified using an empirical model or acomputational model.
 10. The computer readable medium of claim 9,wherein the hot spot is identified using a sensitivity of a pattern ofthe portion, with respect to the processing parameter.
 11. The computerreadable medium of claim 1, wherein the processing parameter is any oneor more selected from: actual substrate stage position and/or tilt,actual reticle stage position and/or tilt, focus, dose, an illuminationparameter, a projection optics parameter, data obtained from metrology,and/or data from an operator of a processing apparatus used in thedevice manufacturing process.
 12. The computer readable medium of claim1, wherein the instructions configured to determine or predict anexistence, a probability of existence, a characteristic, or acombination selected therefrom, of a defect are further configured tosimulate an image, or an expected patterning contour, of the hot spotunder the processing parameter and determine an image parameter orcontour parameter.
 13. The computer readable medium of claim 1, whereinthe instructions configured to identify a hot spot are furtherconfigured to identify a location thereof.
 14. The computer readablemedium of claim 1, wherein the defect is undetectable before thesubstrate is irreversibly processed.
 15. A non-transitory computerreadable medium having instructions recorded thereon, the instructions,when executed by a computer, configured to: determine a processingparameter before processing a substrate or a die of the substrate,wherein the substrate is processed by a device manufacturing process toprocess a pattern onto the substrate or onto the die of the substrate;predict or determine, by a computer hardware system, an existence of adefect, a probability of existence of a defect, a characteristic of adefect, or a combination selected therefrom, using the processingparameter before processing the substrate or the die, and using acharacteristic of the substrate or the die, a characteristic of ageometry of a pattern to be processed onto the substrate or the die, orboth; and adjust the processing parameter based on a prediction or adetermination, obtained in the prediction or determination, so as toeliminate, reduce the probability of existence of, or reduce a severityof, the defect.
 16. A non-transitory computer readable medium havinginstructions recorded thereon, the instructions, when executed by acomputer, configured to: identify a hot spot from a portion of a designlayout to be processed onto a substrate by a device manufacturingprocess; determine or predict, by a computer hardware system, anexistence, a probability of existence, a characteristic, or acombination selected therefrom, of a defect produced from the hot spotusing the device manufacturing process; and determine whether to inspectthe hot spot at least partially based on a determination or a predictionof the existence, the probability of existence, the characteristic, or acombination selected therefrom, of the defect obtained in thedetermination or prediction.
 17. The computer readable medium of claim16, wherein the instructions are further configured to cause inspectionof the substrate at positions of potential defects.